On the thin chalk soils of the eastern Champagne the technique is fast becoming common practice, according to Etienne Pilorgé, regional agronomist with CETIOM, the Paris-based oilseeds research organisation.

Not only can growers cut seed costs but the technique tends to provide more uniform germination and emergence, he explains.

Nearly all the 42,000ha (104,000 acres) of oilseed rape in the area is autumn-sown. "Dry Septembers are the big problem," says Luc Riviére, agronomist with the Champagne Cèrèales co-operative based at Châlons sur Marne. "We are OK two years in three but it is never completely safe."

Access to precision drills

CC is one of the biggest French co-ops, with about 14,000 members. Many also grow sugar beet and so already have access to precision drills, says Mr Riviére.

"Precision sowing means they can use quite small amounts of seed – about 2kg/ha." Most seem willing to accept the slower work rate compared with conventional drilling, he says.

Until recently another advantage has been the ability to apply carbofuran granules to guard against cabbage root fly attack, says Mr Pilorgé. But with the introduction of a seed treatment based on isofenphos (not yet available in the UK) that practice is becoming redundant, he believes.

Depending on row width – often 45cm (18in) – the target of 50 plants a square metre works out at 18-22/m of drill run. Mr Pilorgé believes the lower figure is preferable to avoid lodging.

In the cooler parts of Champagne, where conditions are similar to those on much of the UKs chalk downs, most growers aim to sow by Aug 20. In kinder areas the first week in September is the target, although some are sown as late as Sept 15.